1. Field of the Invention
This invention relates to a key for a keypad. It finds particular, but not exclusive use in portable telecommunications devices such as portable telephones and wireless computers or digital assistants.
2. Description of the Prior Art
Most portable telephones and personal digital assistants (PDAs) require a keypad in order to allow a user to enter operational instructions. Portable telephones, in particular, normally require an alphanumeric keypad consisting of at least 10 keys corresponding to the digits 0 to 9. Two further keys carrying the legends # and * are normally provided also. In addition to these keys, however, it is normal practice to provide further keys corresponding to particular functions of the telephone. These may include on-hook and off-hook keys, and, additionally, menu, cursor (up/down and/or left/right), volume and select keys.
Portable telephones pose a particular problem in the area of user interface design. There is a customer demand to reduce the overall size of the telephone for ease of portability and storage, as well as a need for larger displays to facilitate the display of large amounts of data e.g. Internet browsing. These two factors combined have the effect of reducing the area available on the telephone to accommodate the keypad.
As the key pivots about protrusions 320a and 320b, the protrusions serve to mechanically isolate keydome switch 580a from neighbouring keydome switch 580c, which actuates the xe2x80x98selectxe2x80x99 function. The key 180 and the protrusions 320a and 320b are a unitary structure. When the pressure is sufficient to distort keydome switch 580a, the protrusions 320a and 320b act to ensure that keydome switch 580c is not actuated.
Other devices which may be used to provide input control signals are roller balls or rotary switches. Like the joystick, these devices can be comparatively bulky, difficult to accommodate, difficult to back-light and hard to seal against ingress of dust and water.
According to a first aspect of the present invention there is provided a key assembly for a keypad, arranged to operate each of three switches, the key assembly comprising a key and pivot members disposed to provide respective pivot axes about which the key is pivotable for operation of respective ones of the switches.
Advantageously, a key assembly according to embodiments of the invention allows greater functionality to be incorporated into a smaller space than would be the case if individual keys were supplied for each function.
Preferably, the key assembly is used to provide navigational functionality for a portable telephone. The key may replace separate keys for any combination of up, down, left, right and select functions.
A key assembly according to embodiments of the invention allows a user to operate equipment comprising the key assembly such that mis-keyings are less likely to occur. This is due to the increased mechanical isolation between adjacent switches.
In a preferred embodiment, the user is able to pivot a key about a first axis to operate a first switch. The user is also able to pivot the key about a second, different axis to operate a second switch. Additionally, the user is able to operate a third switch by depressing the key such that it does not pivot. The different tactile experiences of each operation can preferably be enhanced through the use of different tactile materials on the surface of the key, or by providing raised/recessed portions.
In a preferred embodiment, a pivoting action of the key operates a first and second switch. A third switch is operated by depression of the key such that pivoting does not occur.
Preferably, the operation of the key to operate the third switch requires depression of the key in such a way that such depression can be considered as being a position between the two pivoted orientations required to operate the other switches.
In a preferred embodiment, pivoting is achieved through the provision of projections between individual switch actuators.
One of the switch actuators may be arranged to be larger than the other actuators, thus further decreasing the chance of inadvertently operating a neighbouring switch.
In a preferred embodiment, the two pivot axes are parallel.
There are many possible relative positions for the switches, but they may be arranged to be collinear.
Preferably, the key assembly forms part of a keypad for use in an electronic apparatus. The electronic apparatus may be a portable communication device such as mobile telephone, a wireless computer or organizer.
Embodiments of the invention provide a number of advantages over prior art solutions.